The Grenade Launcher is a primary weapon for the Demoman. Grenades arc significantly after being fired, and the distance a round will travel depends on the angle at which it was fired (when shooting long distances, though, it's often better to jump and fire than change the angle of fire much past 45 degrees). Grenades travel approximately 1065 hammer units per second, around 45 miles per hour. Grenades will bounce on any surface, albeit very inelastically, and will only detonate on contact with enemies before the first bounce. Grenades launch to the right of the cross-hair, so you should lead to the left to compensate, this is important especially when in close range with faster classes such as Scouts.

Grenades are timed and will detonate after 2.3 seconds, assuming they don't detonate on impact with an enemy. Direct hits with grenades have very little splash range, and will only damage you if the enemy is face to face with you (whereas grenades that detonate after the first bounce have more splash range, but do a lot less damage). Grenades have the advantage of never suffering from falloff damage; hits at long range will still do full damage. There is a blast radius falloff: the greater the distance from the epicenter of the blast, the less damage will be done (even for critical hits).

Inexperienced Demomen can injure themselves with their grenades. Doing so on purpose to grenade jump is a lot harder than sticky jumping and you won't fly as far. However, it uses much less health, and is good for when you need to jump smaller heights and distances, while the Chargin' Targe is equipped or when you don't want to detonate your stickies.

Damage

Base: 120

Direct Hit:

Any range: 81-111

Critical hit: 280-300

Self damage: 42-73 damage (only from point blank range)

Critical hit: Deals same amount of self damage as a regular grenade (42-73)

After Grenade Bounces:

Any range: 22-64

Critical hit: 190 (Splash at 3 ft/1m: 100 crit)

Self damage: 25-64 (depending on how far you are from the explosion)

Critical hit: Deals same amount of self damage as a regular grenade (25-64)

Note: Explosive damage varies depending on how it hits a player, the larger the classes hit box and the closer you are to the explosion the more damage you will take, the further away from the explosion the less damage you can take. Explosions do the most damage when they happen at the mid point of a player model, the explosion will cover more of the hit box and thus do the most damage. Damages are approximate and determined by community testing.

Function times

Attack Interval: 0.6

Reload Base: 1.24

Additional Reload: 0.6

Explosion Wait: 2.28

Reload base is the time it takes to reload the first ammo. Additional reload is the time it takes to reload each ammo after the first. Explosion wait is how long it takes for a fired grenade to explode when it doesn't have a collision explosion. All times are in seconds. Times are approximate and determined by community testing.

Trivia

Despite being a primary weapon, the Grenade launcher is second in the loadout menu, and is treated as a secondary weapon when crafting.

The grenade launcher's magazine in the PC version holds 4 grenades, yet the model has 6 chambers. This is because originally the Demoman had a maximum clip of 6 along with a larger ammo reserve (as did the soldier) but these counts were reduced in the interests of balance not long after TF2's public release. There are many custom made skins that rectify this problem and only give the magazine 4 chambers. [video]

You can tell when a grenade is about to explode: each second after a grenade is fired a colored ring appears around it. When there are 3 rings it is about to explode (after around 4 seconds).

The Demoman reloads the grenade launcher by placing multiple grenades into a single slot. This is most likely an animation oversight or bug.

Even if you are on the BLU team, reloading with the grenade launcher will still show red sleeves.

The Grenade Launcher is based off the real life M79 Grenade Launcher except that it's been modified to fire 6 grenades without having to reload between each shot and has a revolver-like cylinder carrying the Grenade projectiles.

As seen in the " Meet the Demoman" video the grenades launched at a sentry gun would distract the sentry before re-focusing back on the player. However in-game the grenades do not distract the sentry at all.

Although you will be damaged from your pipe bombs, they will go through you, so you cannot direct pipe yourself.

The Grenade Launcher is the last primary weapon to ever be replaced, being replaced with the Loch n Load.